/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.storageengine.dataregion.wal.utils;

import org.apache.iotdb.db.queryengine.plan.planner.plan.node.write.InsertNode;
import org.apache.iotdb.db.storageengine.dataregion.wal.buffer.WALEntry;
import org.apache.iotdb.db.storageengine.dataregion.wal.buffer.WALEntryValue;
import org.apache.iotdb.db.storageengine.dataregion.wal.exception.MemTablePinException;
import org.apache.iotdb.db.storageengine.dataregion.wal.exception.WALPipeException;
import org.apache.iotdb.db.storageengine.dataregion.wal.node.WALNode;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicReference;

/**
 * This handler is used by the Pipe to find the corresponding {@link InsertNode}. Besides, it can
 * try to pin/unpin the {@link WALEntry}s by the memTable id.
 */
public class WALEntryHandler {

  private static final Logger logger = LoggerFactory.getLogger(WALEntryHandler.class);

  private long memTableId = -1;

  // cached value, null after this value is flushed to wal successfully
  @SuppressWarnings("squid:S3077")
  private volatile WALEntryValue value;

  // wal entry's position in the wal, valid after the value is flushed to wal successfully
  // it's safe to use volatile here to make this reference thread-safe.
  @SuppressWarnings("squid:S3077")
  private final WALEntryPosition walEntryPosition = new WALEntryPosition();

  // wal node, null when wal is disabled
  private WALNode walNode = null;

  private volatile boolean isHardlink = false;
  private final AtomicReference<File> hardlinkFile = new AtomicReference<>();

  public WALEntryHandler(final WALEntryValue value) {
    this.value = value;
  }

  /**
   * Pin the wal files of the given memory table. Notice: cannot pin one memTable too long,
   * otherwise the wal disk usage may too large.
   *
   * @throws MemTablePinException If the memTable has been flushed
   */
  public void pinMemTable() throws MemTablePinException {
    if (walNode == null || memTableId < 0) {
      throw new MemTablePinException("Fail to pin memTable because of internal error.");
    }
    walNode.pinMemTable(memTableId);
  }

  /**
   * Unpin the wal files of the given memory table.
   *
   * @throws MemTablePinException If there aren't corresponding pin operations
   */
  public void unpinMemTable() throws MemTablePinException {
    if (walNode == null || memTableId < 0) {
      throw new MemTablePinException("Fail to pin memTable because of internal error.");
    }
    walNode.unpinMemTable(memTableId);
  }

  public InsertNode getInsertNodeViaCacheIfPossible() {
    try {
      final WALEntryValue finalValue = value;
      return finalValue instanceof InsertNode
          ? (InsertNode) finalValue
          : walEntryPosition.readByteBufferOrInsertNodeViaCacheDirectly().getRight();
    } catch (Exception e) {
      logger.warn("Fail to get insert node via cache. {}", this, e);
      throw e;
    }
  }

  /**
   * Get this handler's value.
   *
   * @throws WALPipeException when failing to get the value.
   */
  public InsertNode getInsertNode() throws WALPipeException {
    // return local cache
    final WALEntryValue res = value;
    if (res != null) {
      if (res instanceof InsertNode) {
        return (InsertNode) res;
      } else {
        throw new WALPipeException("Fail to get value because the entry type isn't InsertNode.");
      }
    }

    // wait until the position is ready
    while (!walEntryPosition.canRead()) {
      try {
        synchronized (this) {
          this.wait();
        }
      } catch (final InterruptedException e) {
        logger.warn("Interrupted when waiting for result.", e);
        Thread.currentThread().interrupt();
      }
    }

    final InsertNode node = isHardlink ? readFromHardlinkWALFile() : readFromOriginalWALFile();
    if (node == null) {
      throw new WALPipeException(
          String.format("Fail to get the wal value of the position %s.", walEntryPosition));
    }
    return node;
  }

  public ByteBuffer getByteBuffer() throws WALPipeException {
    // wait until the position is ready
    while (!walEntryPosition.canRead()) {
      try {
        synchronized (this) {
          this.wait();
        }
      } catch (InterruptedException e) {
        logger.warn("Interrupted when waiting for result.", e);
        Thread.currentThread().interrupt();
      }
    }

    final ByteBuffer buffer = readByteBufferFromWALFile();
    if (buffer == null) {
      throw new WALPipeException(
          String.format("Fail to get the wal value of the position %s.", walEntryPosition));
    }
    return buffer;
  }

  private InsertNode readFromOriginalWALFile() throws WALPipeException {
    try {
      return walEntryPosition.readInsertNodeViaCacheAfterCanRead();
    } catch (Exception e) {
      throw new WALPipeException("Fail to get value because the file content isn't correct.", e);
    }
  }

  private InsertNode readFromHardlinkWALFile() throws WALPipeException {
    try {
      return walEntryPosition.readInsertNodeViaCacheAfterCanRead();
    } catch (Exception e) {
      throw new WALPipeException("Fail to get value because the file content isn't correct.", e);
    }
  }

  private ByteBuffer readByteBufferFromWALFile() throws WALPipeException {
    try {
      return walEntryPosition.readByteBufferViaCacheAfterCanRead();
    } catch (Exception e) {
      throw new WALPipeException("Fail to get value because the file content isn't correct.", e);
    }
  }

  public void setWalNode(final WALNode walNode, final long memTableId) {
    this.walNode = walNode;
    this.memTableId = memTableId;
    walEntryPosition.setWalNode(walNode, memTableId);
  }

  public long getMemTableId() {
    return memTableId;
  }

  public void setEntryPosition(final long walFileVersionId, final long position) {
    this.walEntryPosition.setEntryPosition(walFileVersionId, position, value);
    this.value = null;
    synchronized (this) {
      this.notifyAll();
    }
  }

  public WALEntryPosition getWalEntryPosition() {
    return walEntryPosition;
  }

  public int getSize() {
    return walEntryPosition.getSize();
  }

  public void setSize(final int size) {
    this.walEntryPosition.setSize(size);
  }

  public void hardlinkTo(File hardlinkFile) {
    isHardlink = true;
    this.hardlinkFile.set(hardlinkFile);
  }

  @Override
  public String toString() {
    return "WALEntryHandler{"
        + "memTableId="
        + memTableId
        + ", value="
        + value
        + ", walEntryPosition="
        + walEntryPosition
        + '}';
  }
}
